Pressure balanced compliant seal device

Abstract: A compliant seal device for sealing a high pressure area from a low pressure area. The compliant seal device comprises a base member (120) including an annular base wall (130), a first wall (140) extending radially inward from the base wall (130) proximate the high pressure area and a second wall (150) extending radially inward from the base wall (130) proximate the low pressure area, the base member (120) having a cavity (160) formed therein between the first wall (140) and the second wall (150). The compliant seal device further comprises a plurality of flexible sheet members (170) extending between the first wall (140) and the second wall (150), each of the plurality of flexible sheet members (170) having a base end fixed to the first wall (140) and a moveable free end in sealing engagement with the second wall (150) to substantially enclose the cavity (160) with an adjustable pressure therein.

Description: The present invention relates to a compliant seal device for sealing a high pressure area from a low pressure area, as defined in the preamble of claim 1. A compliant seal of this type is known from DE-A1-1 475 588. Another compliant seal is known from EP-A2-0 473 018. Many classes of machinery use clearance seals to contain a gas under pressure. Often these seals are simple labyrinth seals which break down pressure by using a series of teeth or blades in close proximity to a rotating shaft. Such devices are well known and reliable, but allow high rates of gas leakage. Typically, clearances between the blade tips of a labyrinth seal and the shaft are as high as 0,001 - 0,002 mm per mm (inches per inch) of shaft diameter. Much work has been done to reduce the leakage of labyrinth seals. Typically, the approach of past efforts has been directed toward improved blade geometry (e.g., backward angled blade designs), step seals, or interlocking blade designs to reduce losses. Abradable labyrinth seal designs have also been developed and are employed, particularly, on jet engines. The blades of such abradable seals are initially installed with a line-to-line clearance, and then wear in to their own clearance as the machine rotates. However, after the rotor has gone through an operating history of radial vibration combined with axial excursions, a crescent-shaped clearance is often cut into the abradable seal, and leakage can increase dramatically. In spite of many improved designs, therefore, leakage losses for labyrinth seals continue to represent a considerable energy loss in rotating machinery. Another significant problem with high pressure labyrinth seals is the occurrence of rotordynamic effects. Since high pressure gas is quite dense, a labyrinth seal begins to act as a bearing with high gas pressures, but tends to destabilize the rotor due to a lack of concentricity with the actual machine bearings. Significant effort has been made recently to decrease rotordynamic excitation effects. The product of these efforts includes swirl breaks in front of a labyrinth, reverse swirl inducers, and injecting tangentially non-moving gas into the first stagnant region of the labyrinth. Other work has been concentrated on optimized geometry and creating a rough surface within the labyrinth seal to retard circumferential gas velocity buildup. Also, honeycomb design labyrinth seals have been developed to reduce rotordynamic excitation effects. However, further reduction of rotordynamic effects is needed. As an alternative to the labyrinth seal, applicant has proposed a seal having compliant fingers which ride upon a thin gas or liquid film between the fingers and a rotating shaft. Such a compliant finger seal is disclosed in U.S. Patent No. 5,100,158. The above described technical problem is overcome by a compliant seal according to claim 1. Further advantageous embodiments are laid down in the subclaims. The accompanying drawings are included to provide a further understanding of the invention and illustrate several embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings: FIG. 1 is a perspective view of a compliant seal device in accordance with a first embodiment of the invention; FIG. 2 is a side view of half of the compliant seal device of FIG. 1; FIG. 3(A) is a side view of half of the compliant seal device of FIGS. 1 and 2 having a gap cover between the flexible sheet members; FIG. 3(B) is an end view of the compliant seal device of FIG. 3(A); FIGS. 4(A), 4(B) and 4(C) are a perspective view, a pressure distribution diagram and flow diagram, respectively, of a flexible sheet member of the compliant seal device of FIGS. 1 and 2; FIGS. 5(A) and 5(B) are pressure distribution diagrams of a flexible sheet member during non-rotation and rotation of the shaft, respectively, of the compliant seal device of FIGS. 1 and 2; FIG. 6 is a perspective view of the compliant seal device of FIGS. 1 and 2 having angled flexible sheet members; FIGS. 7(A), 7(B) and 7(C) depict the compliant seal device of FIGS. 1 and 2 with recesses formed in the lower sides of the flexible sheet members; FIG. 8(A) is a force distribution diagram of the compliant seal device of FIGS. 1 and 2; FIG. 8(B) shows the preferred shape of a flexible sheet member having a bend in a direction towards a cavity; FIG. 8(C) is a pressure distribution diagram of the compliant seal device of FIGS. 1 and 2 having the flexible sheet member of FIG. 8(B); FIG. 9 is a side view of half of a compliant seal device including a base member with a second wall having a dam member protruding therefrom according to a second embodiment of the invention; FIG. 10 is a side view of half of a compliant seal device including a base member with a second wall having a dam member protruding therefrom, the dam member having an angled inner surface according to a third embodiment of the invention; FIGS. 11(A) and 11(B) are side views of half of a compliant seal device including a base member with a second wall having a secondary sealing element according to a fourth embodiment of the invention; FIGS. 12(A) and 12(B) are side views of half of a co-rotating or a counter rotating apparatus incorporating the compliant seal device of FIG. 11(A); and FIG. 13 is a side view of half of a static apparatus incorporating the compliant seal device of FIG. 11(A). DETAILED DESCRIPTION OF THE INVENTION Reference will now be made in detail to the presently preferred embodiments of the invention, as illustrated in the accompanying drawings, in which like reference characters designate like or corresponding parts throughout the several drawings. A first embodiment of the invention will now be described with reference to FIGS. 1 and 2. As shown in FIGS. 1 and 2, a compliant seal device 100 is provided for inhibiting the flow of a gas (or liquid) in a stream along a shaft 110. The gas (or liquid) is sealed, for example, within a machine housing (not shown) and has a system pressure of P system . The area outside of the sealed machine housing toward which the sealed gas will tend to leak has a discharge pressure P discharge , the system pressure P system being greater than the discharge pressure P discharge . The compliant seal device 100 comprises a base member 120 including an annular base wall 130, a first wall 140 extending radially inward from the base wall 130 proximate the system pressure P system and a second wall 150 extending radially inward from the base wall 130 proximate the discharge pressure P discharge . The base member 120 further has a cavity 160 formed therein between the first wall 140 and the second wall 150. The base member 120 is removably attached to the machine housing (not shown), as is known to one skilled in the art. Preferably, the base member 120 comprises a material having a high yield strength at high temperatures. For example, the base member 120 can comprise a nickel based alloy such as Inconel® manufactured by Inco Alloys International. It should be understood that the composition of the base member 120 can be varied depending on the particular application with which the compliant seal device 100 is to be used. The compliant seal device 100 further comprises a plurality of flexible sheet members 170 extending between the first wall 140 and the second wall 150 of the base member 120. Each of the plurality of flexible sheet members 170 has a base end fixed to the first wall 140 by welding or other means known in the art, and a moveable free end in sealing engagement with the second wall 150 to substantially enclose the cavity 160 with an adjustable pressure P cavity therein. The base ends of the flexible sheet members 170 are preferably displaced from the shaft 110 by a clearance c . Further, the flexible sheet members 170 preferably have a bend 171 to bias their free ends towards the shaft 110. It is contemplated that the flexible sheet members 170 can have other means to bias their free ends toward the shaft 110 as is known to one skilled in the art. Preferably, the cavity pressure P cavity is slightly reduced with respect to the system pressure P system . Typical values of the cavity pressure P cavity are about 80-90 percent of that of the system pressure P system . As will be explained in more detail below, a nominal force balance is thus achieved in the radial direction of the compliant seal device 100. It is contemplated that the cavity pressure P cavity can be fine tuned, i.e., either raised or lowered, as required, by the use of one or more through ports. For example, to raise the cavity pressure P cavity to, for example, compensate for leakage through the flexible sheet members 170, the compliant seal device 100 can comprise a through port 190 in communication with the cavity 160 and the system pressure P system . Likewise, to lower the cavity pressure P cavity , the compliant seal device 100 can comprise a through port (not shown) in communication with the cavity 160 and the discharge pressure P discharge . It should be appreciated that the flow through these through ports is very small, as compared with a standard labyrinth seal design. Although the free ends of the flexible sheet members 170 can be in sealing engagement with the second side 150 of the base member 120 at, for example, an inner peripheral surface of the second side 150, each of the free ends preferably includes a flange 172 for sealing engagement with an inner surface of the second wall 150. To reduce friction between the flanges 172 and the inner surface of the second wall 150, a lubricant (not shown) such as a TFE, graphite, molydisulfide carbon, or chrome carbide with a solid lubricant can be applied to the flanges 172 and/or the inner surface of the second wall 150. As shown in FIG. 1, the flexible sheet members 170 are annually positioned around the shaft 110 circumferentially spaced from each other and, as explained above, preferably extend toward contact with the shaft 110 at their free ends. To reduce friction between the flexible sheet members 170 and the shaft 110 should they come in contact, a lubricant (not shown) such as a TFE, graphite, molydisulfide carbon, or chrome carbide with a solid lubricant can be applied to the shaft 110 and/or the flexible sheet members 170. As will be explained in more detail below, during rotation of the shaft 110, the flexible sheet members 170 actually "ride" upon a thin film of gas (or liquid) with a clearance h above the surface of the shaft 100. As will also be explained in more detail below, with certain modifications, the flexible sheet members 170 can also "ride" above the surface of the shaft 110 during non-rotating conditions. Preferably, the flexible sheet members 170 comprise a material having a high yield strength at high temperatures. For example, the flexible sheet members 170 can comprise a nickel based alloy such as Inconel. Again, it should be understood that the composition of the flexible sheet members 170 can be varied depending on the particular application with which the compliant seal device 100 is to be used. The flexible sheet members 170 can be about 0,0762-0,3048 mm (0,003-0,012 inch) thick, and are preferably 0,1016-0,2032 mm (0,004-0,008 inch) thick. Further, the flexible sheet members 170 are preferably sized to optimize their hydrostatic and hydrodynamic characteristics. Currently, for a 120,65 mm (4,750 inch) shaft and a differential pressure of 413685,6 N/m 2 (60 psi), seals are being tested with a design clearance h of 0,00508-0,0127 mm (0,0002-0,0005) inch between the flexible sheet members 170 and the shaft 110, and with the flexible sheet members 170 being 8,4328 mm (0,332 inch) wide and being circumferentially spaced 0,1524-0,2032 mm (0,006-0,008 inch) from each other. It should be noted that some gas flow occurs through the circumferential spaces between the flexible sheet members 170. Although this gas flow is relatively small, it may be preferable under certain circumstances to provide a gap cover for sealing the spaces between the flexible sheet members 170. Such a gap cover is depicted in FIGS. 3(A) and 3(B) as strips 180 provided to seal across the circumferential spacings between the flexible sheet members 170. Preferably, the strips 180 have a lighter construction than the flexible sheet members 170 and are made of the same material as the flexible sheet members 170. However, it should be noted that the strips 180 can be made of other materials such as different alloys. Further, the strips 180 are preferably thinner than the flexible sheet members 170. The strips 180 may also be attached to the base member 120 by welding or other means known in the art. In accordance with the invention, each of the flexible sheet members 170 of the compliant seal device 100 includes means, responsive to rotation of the shaft 110, for lifting the flexible sheet members 170 away from the shaft 110. As shown in FIG. 3(B) by way of example and not limitation, this lifting means is represented by a curvature of the flexible sheet members 170 in the same direction as the curvature of the shaft 110, wherein the radius of curvature of the flexible sheet members 170 is preferably greater than the radius of the curvature of the shaft 110. During rotation of the shaft 110, the curvature mismatch crease a hydrodynamic lift-off action due to viscous effects of the gas (or liquid). Under rotating conditions, the lifting means captures gas (or liquid) so that the pressure under the flexible sheet members 170 increases causing the flexible sheet members 170 to bend, and lift-off to occur. The flexible sheet members 170 will ride upon a thin film of gas (or liquid) between the flexible sheet members 170 and the shaft 110, thereby making the flexible sheet members 170 compliant to tolerances in the surface of the shaft 110 and differential thermal and centrifugal growth of the shaft 110, as well as variations in the concentricity between the shaft 110 and seal bores (not shown) and rotational runout of the shaft 110. As the flexible sheet members 170 lift off, they will also twist slightly, as shown by FIG. 5(B), so that their leading edges will operate at a larger clearance than their trailing edges. Typical operating clearances at the leading edges of the flexible sheet members 170 are on the order of 0,00762-0,01778 mm (0,0003-0,0007 inch), while typical clearances at the trailing edges are 0,00254-0,00508 mm (0,0001-0,0002 inch). A typical one of flexible sheet members 170 is shown in FIGS. 4(A), 4(B) and 4(C). For such a flexible sheet member, the pressure distribution during non-rotating conditions is shown in FIGS. 4(B) and 4(C). In FIG. 4(C), the solid lines represent the direction of the flow field of the gas (or liquid), and the dotted lines represent lines of constant pressure between the shaft 110 and the underside of the flexible sheet member 170. FIG. 5(A) shows a typical pressure profile through the central section of an individual one of the flexible sheet members 170 during stationary shaft conditions. As shown in FIG. 5(A), during non-rotating conditions, the pressure in the cavity P cavity above the flexible sheet member 170 is slightly less than the pressure between the shaft 110 and the flexible sheet member 170. Therefore, the flexible sheet member 170 is only very lightly pressed down upon the surface of the shaft 110 during non-rotating conditions. FIG. 5(B) shows a typical pressure distribution through the same section of the flexible sheet member 170 shown in FIG. 5(A) as the shaft 110 rotates. At the edge of the flexible sheet member 170, pressure is equal to the local pressure in the space between the flexible sheet members 170. Between the flexible sheet member 170 and the shaft 100, however, pressure builds up because of viscous hydrodynamic effects. A typical pressure distribution under a rotating condition shows that the pressure radially inside the flexible sheet member 170 is greater than the pressure radially outside the flexible sheet member 170 and the flexible sheet member 170 thus lifts from the shaft 110. As can be seen in FIG. 5(B), the pressure under the leading edge 174 of the flexible sheet member 170 is greater than that under the trailing edge 176. Thus, the clearance H between the shaft 110 and the leading edge 174 is greater than the clearance h at the trailing edge 176. As shown in FIG. 6, to augment the lift-off for a preferred direction of rotation of the shaft 110, the flexible sheet members 170 can be arranged such that their elongated axis is angled with respect to the axis of the compliant seal device 100 (or the shaft 110) and such that their free ends face away from the direction of rotation of the shaft 110. As the shaft 110 rotates, the angling causes capture of gas (or liquid) not only from the free ends of the flexible sheet members 170, but also from the fact that the flexible sheet members 170 are partially wrapped over the diameter of the shaft 110, and act like "foil bearings." The increased pressure causes additional lift-off and clearance of the flexible sheet members 170 from the shaft 110. As shown in FIG. 7(A), to further augment the lift-off for a preferred direction of rotation of the shaft 110, each of the flexible sheet members 170 can include a recess 178 formed on its lower side proximate the shaft 110. The recesses 178 can comprise any one of an open Rayleigh pad, a closed Rayleigh pad, a shrouded Rayleigh pad, and a radial, spiral or angled groove. Alternative designs for the recesses 178 can also be utilized as is known in the art. Further, the recesses 178 can be chemically milled, ion etched or made by other means known in the art. It should be appreciated that this configuration increases the pressure range of the compliant seal device 100 by at least partially pressure balancing the recesses 178 and increases lift-off by incorporating step bearing principles similar to Rayleigh pad designs on face seals. It should also be appreciated that with this configuration, it is possible to provide hydrostatic lift-off under the recesses 178 by slightly lowering the cavity pressure P cavity . Accordingly, a clearance between the flexible sheet members 170 and the shaft 110 can be present even under non-rotating conditions. Because the recesses 178 provide hydrodynamic lift, a mismatch in curvature between the shaft 110 and the flexible sheet members 170 is not necessarily required for hydrodynamic lift-off. Therefore, with this configuration, the flexible sheet members 170 and the shaft 110 can have the same radius of curvature. Nevertheless, each of the flexible sheet members 170 may have both a recess and a mismatch in curvature with the shaft 110, as shown in FIG. 7(B). As shown in FIG. 7(C), a recess 178 according to the invention is typically 0,00508-0,01778 mm (0,0002-0,0007 inch) deep in a 0,1016 - 0,2032 mm (0,004 - 0,008 inch) thick metallic flexible sheet member 170. Preferably, the recess 178 extends to a point along the flexible sheet member 170 just before the flange 172 to allow the system pressure P system to enter underneath the end of the flexible sheet member 170, thereby creating a hydrostatic balancing force which creates an additional lifting force. FIG. 8(A) is a typical force distribution diagram for a single one of the flexible sheet members 170 of the compliant seal device 100 of FIGS. 1 and 2. P design shows the pressure distribution for a design clearance h for which a nominal force balance is designed. If the shaft 110 moves so as to decrease the design clearance h , the pressure distribution under the flexible sheet member 170 changes as shown by P reduced , and the total force under the flexible sheet member 170 increases. Conversely, if the shaft 110 moves so as to increase the design clearance h , the pressure distribution changes as shown by P increased , and the total force under the flexible sheet member 170 decreases. Thus, the cavity 60 with the adjustable pressure P cavity therein serve to hydrostatically balance the flexible sheet members 170. It should be appreciated that the principle of hydrostatic balance used for this design is much the same as for hydrostatically balanced gas face seals. Similarly, hydrodynamic force increases are expected at operating conditions, much as the way in which spiral grooves work on a gas face seal. It should also be appreciated that once a nominal force balance is achieved, the fast response action of the recesses 178 can come into play, as discussed above. Thus, when the shaft 110 rotates, the recesses 178 formed in the flexible sheet members 170 create additional force, slightly increasing the operating film height. Although this may slightly increase leakage, it gives rise to a much higher film stiffness. It should be noted that in order to generate hydrodynamic lift-off of the flexible sheet member 170 during rotating conditions, it is desired that under static conditions, the flexible sheet member 170 lie very close, e.g., 0,000635-0,00254 mm (0,000025-0,0001 inch), to the surface of the shaft 110. In this manner, the hydrodynamic forces can be fully developed underneath the flexible sheet member 170. However, because the first point of contact between the flexible sheet member 170 and the shaft 110 during non-rotating conditions is at the most flexible point of the flexible sheet member 170, namely, the point just before the flange 172, the compliant seal device 100 behaves like a tip seal whenever shaft run out occurs. This not only provides for unstable hydrodynamic lift-off conditions which increase leakage of the compliant seal device 100, but also prevents the compliant seal device 100 from accommodating large excursions of the shaft 110. Accordingly, as shown in FIG. 8(B), the flexible sheet member 170 preferably has a bend 173 in a direction toward the cavity 160 such that the first point of contact p of the flexible sheet member 170 with the shaft 110 is away from the flange 172. Preferably, the point p is located about 2/3 the length of the flexible sheet member 170. By locating the point p away from the flange 172, a length l of the flexible sheet member 170 can be in contact with the surface of the shaft 110 during non-rotating conditions because of the lack of any pressure forces underneath the flexible sheet member 170 along the length l . It should be understood that FIG. 8(B) shows the flexible sheet member 170 as manufactured, and when the point p first contacts the shaft 110. Pressure in the cavity 160 over the length l will then cause the length l to lay down on the shaft 110. It should be appreciated that with this design, the compliant seal device 100 has good contact with the surface of the shaft 110 during non-rotating conditions regardless of the system pressure P system . Moreover, with this design, the compliant seal device 100 can handle relatively large shaft excursions, e.g., 0,889 mm (0,035 inch), and the hydrodynamic lift-off forces are no longer concentrated at a single point but, instead, are spread over the length l of the flexible sheet member 170, as shown by FIG. 8(C). A second embodiment of the invention will now be described with reference to FIG. 9. As shown in FIG. 9, a compliant seal device 200 is provided comprising a base member 220, the base member 220 including an annular base wall 230, a first wall 240 extending radially inward from the base wall 230 proximate a system pressure P system and a second wall 250 extending radially inward from the base wall 230 proximate a discharge pressure P discharge . The base member 220 further includes a cavity 260 formed therein between the first wall 240 and the second wall 250. The compliant seal device 200 further comprises a plurality of flexible sheet members 270 extending between the first wall 240 and the second wall 250. Each of the plurality of flexible sheet members 270 has a base end fixed to the first wall 240 and a flange 272 in sealing engagement with the second wall 250 to substantially enclose the cavity 260 with an adjustable pressure P cavity therein. As in the first embodiment, the cavity pressure P cavity can be fine tuned by the use of a through port 290 in communication with the cavity 260 and the system pressure P system , or a through port (not shown) in communication with the cavity 260 and the discharge pressure P discharge . Preferably, the compliant seal device 200 is the same as the compliant seal device 100 of FIG. 2 except that the inner surface 252 of the second wall 250 includes a dam member 254 protruding therefrom. The dam member 254 defines a space 256 between the flanges 272 of the flexible sheet members 270 and the inner surface 252 of the second wall 250 to maintain a pressure balance on opposite sides of the flanges 272. It should be appreciated that with this design, the frictional forces between the second wall 250 and the flanges 272 can be reduced. Further, the dam member 254 serves to protect the flexible sheet members 270, for example, during assembly of the compliant seal device 200. A third embodiment of the invention will now be described with reference to FIG. 10. As shown in FIG. 10, a compliant seal device 300 is provided comprising a base member 320, the base member 320 including an annular base wall 330, a first wall 340 extending radially inward from the base wall 330 proximate a system pressure P system and a second wall 350 extending radially inward from the base wall 330 proximate a discharge pressure P discharge . The base member 320 further includes a cavity 360 formed therein between the first wall 340 and the second wall 350. The compliant seal device 300 further comprises a plurality of flexible sheet members 370 extending between the first wall 340 and the second wall 350. Each of the plurality of flexible sheet members 370 has a base end fixed to the first wall 340 and a flange 372 in sealing engagement with the second wall 350 to substantially enclose the cavity 360 with an adjustable pressure P cavity therein. As in the first embodiment, the cavity pressure P cavity can be fine tuned by the use of a through port 390 in communication with the cavity 360 and the system pressure P system , or a through port (not shown) in communication with the cavity 360 and the discharge pressure P discharge . The compliant seal device 300, like the compliant seal device 200 of FIG. 9, includes a dam member 354 protruding therefrom. The dam member 354 defines a space 356 between the flanges 372 of the flexible sheet members 370 and the inner surface 352 of the second wall 350 to maintain a pressure balance on opposite sides of the flanges 372. Preferably, the compliant seal device 300 is the same as the compliant seal device 200 of FIG. 9 except that an inner surface of the dam member 354 is angled for selective engagement with the flanges 372 of the flexible sheet members 370 as the free ends of the flexible sheet members 370 move. It should be appreciated that with this design, the angled inner surface approximates a spherical surface thereby minimizing the friction forces generated at the interface between the flanges 372 and the second wall 350. A fourth embodiment of the invention will now be described with reference to FIGS. 11(A) and 11(B). As shown in FIG. 11(A), a compliant seal device 400 is provided comprising a base member 420, the base member 420 including an annular base wall 430, a first wall 440 extending radially inward from the base wall 430 proximate a system pressure P system , and a second wall 450 extending radially inward from the base wall 430 proximate a discharge pressure P discharge . The base member 420 further includes a cavity 460 formed therein between the first wall 440 and the second wall 450. The compliant seal device 400 further comprises a plurality of flexible sheet members 470 extending between the first wall 440 and the second wall 450. Each of the plurality of flexible sheet members 470 has a base end fixed to the first wall 440 and flange 472 in sealing engagement with the second wall 450 to substantially enclose the cavity 460 with an adjustable pressure P cavity therein. As in the first embodiment, the cavity pressure P cavity can be fine tuned by the use of a through port 490 in communication with the cavity 460 and the system pressure P system , or a through port (not shown) in communication with the cavity 460 and the discharge pressure P discharge . Preferably, the compliant seal device 400 is the same as the compliant seal device 100 of FIG. 2 except that the inner surface 452 of the second wall 450 includes a secondary sealing element. For example, as shown in FIG. 11(A), the secondary sealing element can include an O-ring 456 contained within a recess 454 formed in the inner surface 452 of the second wall 450. Similarly, as shown in FIG. 11(B), the secondary sealing element can include a spring energized TEFLON seal 458 contained within the recess 454 formed in the inner surface 452 of the second wall 450. It should be understood that other secondary sealing elements can be used as is known in the art. It should be appreciated that with this design, the friction forces between the second wall 450 and the flanges 472 can be reduced. A seal according to any of the foregoing embodiments shows improved sealing compared to both prior labyrinth seals and compliant seals. In addition, the present invention provides for improved hydrostatic and hydrodynamic force balancing, thereby minimizing rotordynamic excitation effects by transmitting minimum radial force to the shaft. Still further, once a nominal force balance is achieved, the present invention allow for a very high frequency force balance response. Additional advantages and modifications will readily occur to those skilled in the art. For example, although the foregoing embodiments have been described with respect to an annularly shaped seal, the teachings of the present invention can also be applied toward linear seals. Further, the teachings of the present invention can be applied toward co-rotating, counter rotating, and static sealing applications. With respect to co-rotating and counter rotating sealing applications, it is contemplated that any of the compliant seal devices described thus far can be used to seal to a high pressure area from a low pressure along a gap between two co-rotating or two counter rotating members. For example, as shown in FIG. 12(A), the compliant seal device 400 of FIG. 11(A) can be provided for sealing a system pressure P system from a discharge pressure P discharge along a gap g between a first rotating member 500 and a second rotating member 510. The first rotating member 500 and the second rotating member 510 can comprise, for example, outer and inner rotors, respectively, of a co-rotating or a counter rotating aircraft engine. Further, the first and second rotating members 500 and 510 can rotate at either different speeds or at the same speed. In a co-rotating engine, the first and second rotating members 500 and 510 rotate in the same direction relative to one another, whereas in a counter rotating engine, the first and second rotating members 500 and 510 rotate in opposite directions relative to one another. Such co-rotating and counter rotating engines are manufactured by, for example, Pratt & Witney and General Electric. Although FIG 12(A) shows the compliant seal device 400 mounted on the first rotating member 500, the compliant seal device 400 can be mounted on the second rotating member 510 as shown in FIG. 12(B). With respect to static sealing applications, it is contemplated that any of the compliant seal devices described thus far can be used to seal a high pressure area from a low pressure along a gap between two stationary members. For example, as shown in FIG. 13, the compliant seal device 400 of FIG. 11(A) can be provided for sealing a system pressure P system from a discharge pressure P discharge along a gap g between a first stationary member 520 and a second stationary member 530. The first stationary member 520 and the second stationary member 530 can comprise, for example, a metallic casing and a ceramic nozzle, respectively, of an aircraft engine or steam turbine. Generally, the two members will typically have different thermal coefficients and thus experience different degrees of radial thermal expansion during operation. By providing the compliant seal device 400 in the manner shown in FIG. 13, the compliant seal device 400 can compensate for differential thermal expansion between the first and second stationary members 520 and 530. Therefore, the invention is not limited to the specific details, representative devices, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope of the appended claims.

Claims: Compliant seal device for sealing a high pressure area from a low pressure area, the compliant seal device comprising: a base member (120,220,320,420) including a base wall (130,230,330,430), the base member (120,220,320,420) having a cavity (160,260,360,460) formed therein; and a flexible sheet member (170,270,370,470) having a base end fixed to the base member (120,220,320,420) and a movable free end in sealing engagement with the base member (120,220,320,420) to substantially enclose the cavity (160,260,360,460) with an adjustable pressure therein, wherein the base member (120,220,320,420) further comprises a first wall (140,240,340,440) extending from said base wall (130,230,330,430) proximate the high pressure area and a second wall (150,250,350,450) extending from said base wall (130,230,330,430) proximate the low pressure area, said cavity (160,260,360,460) being formed between said first wall and said second wall (150,250,350,450), characterized in that the flexible sheet (170,270,370,470) is fixed to the first wall (140,240,340,440) with its base end and is in sealing engagement with the second wall (150,250,350,450)) with its movable free end, and that said seal device (100,200,300,400) has a through port in one of said first and second walls (140,240,340,440;150,250,350,450) for establishing fluid communication between the cavity (160,260,360,460) and either with the high pressure side or the low pressure side, the through port being dimensioned so as to allow for adjusting the pressure inside the cavity (160,260,360,460). Compliant seal device according to claim 1, wherein the free end of the sheet member includes a flange (172,272,372,472) for sealing engagement with an inner surface of the second wall (150,250,350,450). Compliant seal device according to claim 2, wherein a lubricant is provided between the flange (172,272,372,472) and the inner surface of the second wall (150,250,350,450). Compliant seal device according to claim 2 or 3, wherein the inner surface of the second wall (250,350) includes a dam member (254,354) protruding therefrom, the dam member defining a space between the flange (272,372) and the inner surface of the second wall to maintain a pressure balance on opposite sides of the flange. Compliant seal device according to claim 4, wherein an inner surface of the dam member (354) is angled for selective engagement with the flange (372) as the free end of the sheet member is moved. Compliant seal device according to claim 2, wherein the inner surface of the second wall (450) includes a secondary sealing element (456) for sealing engagement with the flange (472). Compliant seal device according to claim 6, wherein the secondary sealing element (456) includes any one of an O-ring and a spring-energized compound seal contained within a recess formed in the inner surface of the second wall (450). Compliant seal device according to one of claims 1 to 7, wherein the pressure within the cavity (160,260,360,460) is about 80 to 90 percent of a pressure within the high pressure area. Compliant seal device according to one of claims 1 to 8, wherein the flexible sheet member (170) has an upper side proximate the cavity (160) and a lower side opposite the upper side, the lower side of the flexible sheet member (170) having a recess (178) formed therein. Compliant seal device according to claim 9, wherein the recess (178) comprises any one of an open Rayleigh pad, a closed Rayleigh pad, a shrouded Rayleigh pad, a radial groove, and a spiral groove. Compliant seal device according to one of claims 1 to 10, wherein the flexible sheet member (170,270,370,470) has an elongated axis in an axial direction and wherein the elongated axis is angled with respect to a central axis of the compliant seal device. Compliant seal device according to one of claims 1 to 11, wherein the flexible sheet member (170,270,370,470) has a bend in a direction towards the cavity (160,260,360,460). Compliant seal device according to one of claims 1 to 12, wherein said base wall (130,230,330,430) of said base member is an annular base wall, said first wall (140,240,340,440) extends radially inward from the base wall, said second wall (150,250,350,450) extends radially inward from the base wall, and wherein a plurality of flexible sheet members (170,270,370,470) extends between the first wall and the second wall, each of the plurality of flexible sheet members having a base end fixed to the first wall and a moveable free end in sealing engagement with the second wall to substantially enclose the cavity with an adjustable pressure therein. Compliant seal device according to claim 13, wherein the plurality of sheet members (170) are circumferentially spaced from each other, and further wherein a gap cover (180) is attached to the first wall (140) radially outside of the sheet members to cover the circumferential spaces between the sheet members. Apparatus having a high pressure area and a low pressure area, the apparatus comprising a first member (500,520) and a second member (510,530), and a compliant seal device according to one of claims 1 to 14, for sealing the high pressure area from the low pressure area between said first and second member. Apparatus according to claim 15, wherein each of the plurality of flexible sheet members (170,270,370,470) includes lifting means, responsive to rotation of one of said members (500,510), for lifting the flexible sheet member away from one of said members. Apparatus according to claim 15 or 16, wherein said first member (520) is a first stationary member, and wherein said second member (530) is a second stationary member. Apparatus according to claim 15 or 16, wherein said first member (500) is a first rotating member, and wherein said second member (510) is a second rotating member. Apparatus according to claim 18, wherein the first rotating member (500) rotates in a first direction and the second rotating member (510) rotates in a second direction opposite the first direction. Apparatus according to claim 18, wherein the first rotating member (500) and the second rotating member (510) rotate in a first direction.

Inventors: GARDNER JAMES F, MA HAI-PING, GARDNER, JAMES F., MA, HAI-PING
Applicants: EG & G INC, EG & G, INC.
Application year: 1994
Main classification: F16J15
IPC codes: F16J15